Storage

Vol. 1 No. 4 – June 2003

Storage

Interviews

A Conversation with Jim Gray

Sit down, turn off your cellphone, and prepare to be fascinated. Clear your schedule, because once you've started reading this interview, you won't be able to put it down until you've finished it.

A Conversation with Jim Gray

Sit down, turn off your cellphone, and prepare to be fascinated. Clear your schedule, because once you’ve started reading this interview, you won’t be able to put it down until you’ve finished it.

Opinion

Big Storage: Make or Buy?

We hear it all the time. The cost of disk space is plummeting.

Big Storage:Make or Buy?
Josh Coates, Scale8 Inc.

We hear it all the time. The cost of disk space is plummeting. Your local CompUSA is happy to sell you a 200-gigabyte ATA drive for $300, which comes to about $1,500 per terabyte. Go online and save even more—$1,281 for 1 terabyte of drive space (using, say, 7X Maxtor EIDE 153-GB ATA/113 5400-RPM drives).

So why would anyone pay $360,000 to XYZ Storage System Corp. for a 16-terabyte system? I mean, what’s so hard about storage? Good question.

by Josh Coates

Articles

DAFS: A New High-Performance Networked File System

This emerging file-access protocol dramatically enhances the flow of data over a network, making life easier in the data center.

DAFS: A New High-Performance Networked File System

This emerging file-access protocol dramatically enhances the flow of data over a network, making life easier in the data center.

Steve Kleiman, Network Appliance

The Direct Access File System (DAFS) is a remote file-access protocol designed to take advantage of new high-throughput, low-latency network technology.

The motivation for the new protocol comes from three technology trends that have emerged in the past several years:

by Steve Kleiman

Storage Systems: Not Just a Bunch of Disks Anymore

The concept of a storage device has changed dramatically from the first magnetic disk drive introduced by the IBM RAMAC in 1956 to today's server rooms with detached and fully networked storage servers. Storage has expanded in both large and small directions - up to multi-terabyte server appliances and down to multi-gigabyte MP3 players that fit in a pocket. All use the same underlying technology - the rotating magnetic disk drive - but they quickly diverge from there.

Storage Systems
Not Just a Bunch of Disks Anymore
ERIK RIEDEL, SEAGATE RESEARCH

The sheer size and scope of data available today puts tremendous pressure on storage systems to perform in ways never imagined.

The concept of a storage device has changed dramatically from the first magnetic disk drive introduced by the IBM RAMAC in 1956 to today’s server rooms with detached and fully networked storage servers. Storage has expanded in both large and small directions—up to mulit-terabyte server appliances and down to multi-gigabyte MP3 players that fit in a pocket. All use the same underlying technology—the rotating magnetic disk drive—but they quickly diverge from there.

Here we will focus on the larger storage systems that are typically detached from the server hosts—the specialized appliances that form the core of data centers everywhere. We will introduce the layers of protocols and translations that occur as bits make their way from the magnetic domains on the disk drives and interfaces—around the corner or around the world—to your desktop.

by Erik Riedel

The Emergence of iSCSI

When most IT pros think of SCSI, images of fat cables with many fragile pins come to mind. Certainly, that's one manifestation - the oldest one. But modern SCSI, as defined by the SCSI-3 Architecture Model, or SAM, really considers the cable and physical interconnections to storage as only one level in a larger hierarchy. By separating the instructions or commands sent to and from devices from the physical layers and their protocols, you arrive at a more generic approach to storage communication.

The Emergence of iSCSI

Modern SCSI, as defined by the SCSI-3 Architecture Model, or SAM, really considers the cable and physical interconnections to storage as only one level in a larger hierarchy.

Jeffrey S. Goldner, Microsoft Corporation

When most IT pros think of SCSI, images of fat cables with many fragile pins come to mind. Certainly, that's one manifestation—the oldest one. But modern SCSI, as defined by the SCSI-3 Architecture Model, or SAM, really considers the cable and physical interconnections to storage as only one level in a larger hierarchy. By separating the instructions or commands sent to and from devices from the physical layers and their protocols, you arrive at a more generic approach to storage communication.

Separating the wire protocol from the command protocol allows a common representation of SCSI independent of the actual physical carrier. The various command sets defined in the SCSI-3 protocol command suite all standardize the format of the commands and responses from the targets.

by Jeffrey S. Goldner

You Don't Know Jack about Disks

Magnetic disk drives have been at the heart of computer systems since the early 1960s. They brought not only a significant advantage in processing performance, but also a new level of complexity for programmers. The three-dimensional geometry of a disk drive replaced the simple, linear, address space tape-based programming model.

You Don’t Know Jack About Disks
DAVE ANDERSON, SEAGATE TECHNOLOGY

Whatever happened to cylinders and tracks?

Magnetic disk drives have been at the heart of computer systems since the early 1960s. They brought not only a significant advantage in processing performance, but also a new level of complexity for programmers. The three-dimensional geometry of a disk drive replaced the simple, linear, address spacetape-based programming model.

Traditionally, the programmer’s working model of disk storage has consisted of a set of uniform cylinders, each with a set of uniform tracks, which in turn hold a fixed number of 512-byte sectors, each with a unique address. The cylinder is made up of concentric circles (or tracks) on each disk platter in a multiplatter drive. Each track is divided up like pie slices into sectors. Because any location in this three-dimensional storage space could be uniquely identified by the cylinder number, head (surface) number, and sector number, this formed the basis for the original programming model for disk drives: cylinder-head-sector access.

by Dave Anderson